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Genetic requirements for M oraxella catarrhalis growth under iron‐limiting conditions
Author(s) -
Vries Stefan P. W.,
Burghout Peter,
Langereis Jeroen D.,
Zomer Aldert,
Hermans Peter W. M.,
Bootsma Hester J.
Publication year - 2013
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12081
Subject(s) - biology , mutant , complementation , gene , moraxella catarrhalis , phenotype , genetics , operon , microbiology and biotechnology , transcriptome , moraxella (branhamella) catarrhalis , genetic screen , gene expression , haemophilus influenzae , bacteria
Summary Iron sequestration by the human host is a first line defence against respiratory pathogens like M oraxella catarrhalis , which consequently experiences a period of iron starvation during colonization. We determined the genetic requirements for M . catarrhalis BBH 18 growth during iron starvation using the high‐throughput genome‐wide screening technology genomic array footprinting ( GAF ). By subjecting a large random transposon mutant library to growth under iron‐limiting conditions, mutants of the MCR _0996‐ rhlB ‐ yggW operon, rnd , and MCR _0457 were negatively selected. Growth experiments using directed mutants confirmed the GAF phenotypes with Δ yggW (putative haem‐shuttling protein) and Δ MCR _0457 (hypothetical protein) most severely attenuated during iron starvation, phenotypes which were restored upon genetic complementation of the deleted genes. Deletion of yggW resulted in similar attenuated phenotypes in three additional strains. Transcriptional profiles of Δ yggW and Δ MCR _0457 were highly altered with 393 and 192 differentially expressed genes respectively. In all five mutants, expression of nitrate reductase genes was increased and of nitrite reductase decreased, suggesting an impaired aerobic respiration. Alteration of iron metabolism may affect nasopharyngeal colonization as adherence of all mutants to respiratory tract epithelial cells was attenuated. In conclusion, we elucidated the genetic requirements for M . catarrhalis growth during iron starvation and characterized the roles of the identified genes in bacterial growth and host interaction.